Chinese patent CN1303717 (application no. CN99126047.3), published on Jul. 18, 2001 described a transdermal drug delivering device. The application disk is applied on the skin and press the drug into the skin to treat. When the device is used to treat, the application disk is applied on the skin, and the outer annular cavity raise up the skin by absorptive force caused by the negative pressure because the outer annular cavity is communicated with the negative pressure source, and then the application disk is applied on the skin, at the same time, the central cavity is sealed completely, volatile constituent of the drug placed in the central cavity cannot escape out. In actual use, the application disk is prone to falling off in some situation:
1. The top of the outer annular cavity and the top of the central cavity is one flat or curve surface which connected closely. Because the application disk has a certain thickness and the top thereof is a distance from the skin, the application disk can be applied firmly on the portion flat of the body. However, when the application disk is applied on a portion out of flatness, such as nape, leg and arm which portion curvature is bigger, the top of the central cavity of the application disk will apply a great force to the top of the outer cavity, so that the absorptive force of the outer annular cavity caused by negative pressure is weakened, and the application disk is prone to falling off, and the treatment is affected.
2. the temperature in the central cavity is increased gradually due to being heated by the skin and/or outer heat source, and the volatilization of the drug is released gradually, so that the pressure of the central cavity is increased gradually and accelerate the transdermal delivering of the drugs. The increased pressure apply a outward raising force to the top of the central cavity. When the pressure is relative great, the top will extrude and produce a great force to the top of the outer cavity. The absorptive force of the outer annular cavity caused by negative pressure is weakened, and the application disk is prone to falling off, and the treatment is affected.
3. The vacuum tube is arranged on the top of the outer annular cavity in this solution. During the treatment, when the vacuum is stretched, for example being touched accidentally, the stretch force applied on the vacuum tupe will be delivered to the annular outer wall through the top of the annular outer cavity, therefore, the absorptive force caused by negative pressure is weakened and the application disk is prone to falling off and the treatment is affected.